Hydraulic jack



Dec. 12, 1961 w. B. WESTCOTT, JR 3,012,403

HYDRAULIC JACK Filed Sept. 3, 1959 I 3o 23 1 2| 22 I v 36 37 17 W l J FIG. 2

IN V EN TOR.

WILLIAM B. WESTCOTTJR.

ATTORNEY United States Patent Ofiice 3,012,403 Patented Dec. 12, 1961 3,012,403 HYDRAULIC JACK William B. Westcott, Jr., Cleveland Heights, Ohio, assiguor to Cleveland Pneumatic Industries, Inc, Cleveland, Ohio, a corporation of Ohio Filed Sept. 3, 1959, Ser, No. 837,923 2 Claims. (Cl. 6051) This invention relates to hydraulic jack and more particularly to a hydraulic jack operated from a pressure source of compressed liquid.

in many applications, it is necessary to provide a small jack that can be inserted and used in confined locations which is capable of lifting very large loads. This is particularly true for jacks for larger aircraft since they have to be placed between closely spaced wheels. It is also desirable that such jacks be arranged so that they can be operated by other than manual means since it is time consuming to manually jack such large loads.

It is an important object of this invention to provide a hydraulic jack combination which is operated by compressed liquid contained within an accumulator.

It is another object of this invention to provide an accumulator jack combination which is portable so that it can be used at locations where power is not available.

It is still another object of this invention to provide a hydraulic jack system which operates at high pressures.

Further objects and advantages will appear from the following description and drawings, wherein:

FIGURE 1 is a side elevation partially in section showing a preferred structure of a jack incorporating this invention and its hydraulic connections; and

FIGURE 2 is a side elevation illustrating the complete jacking system which includes the jack, the reservoir, and the accumulator.

In the past, it has been customary to use manually operated hydraulic jacks to jack aircrafts when the wheels had to be changed or serviced. The increased size of present day aircraft has made such a system unsatisfactory for two reasons. First, there is a limit in the pressure that can be practically obtained by manual pumping. Since the pressure determines the size of jack which will be necessary for a given load, this maximum pressure limit has resulted in increasing sizes of jack to the point where it is now difiicult to fit the jack between the wheels on the landing gear. Second, the extreme Weight of the larger aircraft has resulted in increased energy requirements so that manual jacking is not only difficult but time consuming. Since it is necessary to quickly service aircrafts to maintain schedules, such time consuming operations are undesirable.

In a jack according to this invention, an accumulator is pressurized with liquid compressed to pressures in the order of 60,000 to 70,000 pounds per square inch. At such pressures, silicone oils and normal hydraulic fluids are capable of substantial compression in the order of 15 to 20 percent depending on the particular oil used. At such pressures, large amounts of potential energy can be stored within very small accumulators. Because of the extreme pressure, the jack itself can be designed with a minimum size and weight for a given load capacity and the difficulty of using the jack in confined locations is substantially eliminated.

Referring to the drawings, the jack itself includes a body formed with an axial cylinder bore 11 into which proiects a piston 12. A seal assembly 13 is mounted at the open end of the cylinder bore 12 by a gland nut 14 to provide sealing engagement between the body 10 and the piston 12. The seal assembly 13 is preferably of the differential area type disclosed in the patent to Bingham, No. 2,308,149, which will operate at the high pressures.

The piston 12 and cylinder bore 11 co-operate to define a. chamber 16 the volume of which is increased by movement of the piston 12 upward and out of the body 10. The lower end of the body 10 should be formed with an. enlarged base 17 so that the reaction of the jack can be spread over sulficient area to prevent damage to the runway and the upper end of the piston. 12 provided with a head 18 adapted to engage the load to be lifted.

An accumulator 19 is preferably formed as a sphere.

so that it will have the maximum strength and capacity for a given weight and is adapted to be completely filled and pressurized with liquid to pressures in the order of 60,000 to 70,000 pounds per square inch. A valve 21 is threaded onto the accumulator 19 and connects to a quick disconnect 22 through a high pressure line 23. The quick disconnect is in turn connected through a ball type back check valve 24 and a passage 26 in the body 10 to the chamber 16. Thus, when the valve 21 is opened, fluid pressure is admitted from the accumulator 19 into the chamber 16 but the back check valve 24 prevents flow in the opposite direction out of the chamber 16. The quick disconnect 22 is provided so that the accumulator 19 can be disconnected from the jack and connected to a suitable pump for pressurizing or to permit the substitution of other fully charged accumulators.

In order to conserve the energy of the accumulator 19, a manual pump is provided to bring the head 18 into engagement with the load manually. This pump, which is preferably high capacity when compared to the diameter of the cylinder bore 11, can be quickly operated to eX- tend the piston 12 into a position against the load before the valve 21 is opened. The pump includes a piston 27 slidable in a second cylinder bore 28 in the body 10. A normal O-ring type seal 29 is mounted on the piston 27 to provide sealing engagement between the cylinder bore 28 and the piston 27. A pump handle 25 is pivoted on the body 10 and connected to the piston 27 by a connectin rod 30 so that the piston 27 can be manually operated by pumping the handle 25. The piston 27 and the cylinder bore 28 co-operate to define a pumping chamber 31. The chamber 31 is connected to the chamber 16 through a back check valve 32 and a passage 33 so that liquid can flow in a direction from the chamber 31 to the chamber 16 and cannot flow in the opposite direction. A second back check valve 34 is open to the chamber 31 and a hydraulic line 36 which in turn connects to a reservoir 37. A manually operated valve 38 is connected through by-pass passages 39 and 41 to permit flow from the chamber 16 to the line 36 and reservoir 37 when it is opened.

In operation, the body 10 is positioned so that the head 18 is located under the load to be raised. The valve 38 is closed. The accumulator 19 is then connected by means of the quick disconnect 22 to the jack with the valve 21 closed. The pump handle 25 is then operated to pump liquid from the reservoir 37 into the chamber 16 and raise the piston 12 until the head 18 engages the load. When the head 18 engages the load, the chamber 16 is filled with liquid at a relatively low pressure. The valve 21 is then opened to admit high pressure liquid from the accumulator 19 into the chamber 16. The high pressure liquid operates to raise the piston 12 relative to the body 10 and in turn raise the load. When the load has been raised to the desired amount, the valve 21 is closed and the load is supported by the column of high pressure liquid Within the chamber 16. When it is desired to lower the jack, the valve 38 is opened to permit the high pressure liquid to flow into the reservoir 37.

in order to provide a system wherein the accumulator does not become excessive in size and therefore difiicult to handle, the accumulator should be sized to store only sufficient energy to operate the jack under maximum load conditions through one operation. This does not present difiiculties since additional fully charged accumulators can be used for subsequent operation of the jack. If the jack is used under loads below the maximum design load, the pressure within the chamber 16 will not be as high so the accumulator need not be pressurized to the maximum pressure. Generally speaking, the accumulator and jack will be sized so that the sufiicieut volume of liquid will be available in the accumulator to raise the piston 12 to its maximum stroke and maintain a pressure in the chamber 16 in the order of 40,000 pounds. Thus, a jack is provided 'WhCI'ClH' each square inch of piston cross section provides a 40,000 pound load carrying capacity.

Because the hydraulic line 36 is never exposed to high pressure, it can be a suitable fiexiblelow pressure type. However, the high pressure line 23 must be capable of withstanding the accumulator pressures. Normally, this line will be heavy wall tubing with a small diameter and should be formed with a loop to provide flexibility. Since the Wall thickness for a given pressure is the function of the diameter of a tube, it is desirable to use small diameter tubing to increase flexibility and reduce weight. Also, the valve 21 and the quick disconnect 22 should be small so that the high pressures will not require excessive Wall thicknesses. Small valves and small diameter tubing can be used since the flow rates are small.

Although a preferred embodiment of this invention is illustrated, it will be realized that various modifications of the structural details may be made without departing from the mode of operation and the essence of the invention. Therefore, except insofar as they are claimed in 'the appended claims, structural details may be varied widely without modifying the mode of operation. Accordingly, the appended claims and not the aforesaid detailed description are determinative of the scope of the invention.

I claim:

1. A jack comprising a jack cylinder, a jack piston supported in said cylinder for movement in opposite directions relatively to said cylinder, a first liquid reservoir, a mass of liquid contained in said first liquid reservoir at high pressure, a pressure line connecting said first liquid reservoir to the jack cylinder for introducing liquid at' high pressure from the first liquid reservoir into the jack cylinder to move the jack piston relatively to the jack cylinder, a normally closed valve in said pressure line adapted to be opened for flow of liquid at high pressure from said first liquid reservoir to said jack cylinder, at check valve in said pressure line permitting flow of liquid at high pressure only from said first liquid reservoir to the jack cylinder, a second liquid reservoir, a mass of liquid contained in said second reservoir at atmospheric pressure, a liquid delivery line for connecting said second reservoir to the jack cylinder, a pump interposed in said delivery line for the reception of liquid from said second reservoir and for pumping said liquid into said jack cylinder to produce movement of the jack piston relatively to the jack cylinder, said pressure line and said delivery line being independent of each other for introducing liquid into the cylinder from either the first liquid reservoir or from the second liquid reservoir, a bypass line connected to said jack cylinder and connected to the delivery line at a point by-passing the pump, a by-pass valve normally maintaining said by-pass line closed and adapted to be opened to release liquid from the jack cylinder through the by-pass line and the delivery line for return of liquid from the jack cylinder to the second liquid reservoir.

2. A jack comprising a jack cylinder, a jack piston supported in said cylinder for movement in'opposite directions relatively to said cylinder, a first liquid reservoir, a mass of liquid contained in said first liquid reservoir at high pressure, a pressure line connecting said first liquid reservoir to the jack cylinder for introducing liquid at high pressure from the first liquid reservoir into the jack cylinder to move the jack piston relatively to the jack cylinder, a normally closed valve in said pressure line adapted to be opened for flow of liquid at high pressure from said first liquid reservoir to said jack cylinder, a check valve in said pressure line permitting fioW of liquid at high pressure only from the first liquid reservoir to the jack cylinder, a quick-disconnect device in said pressure line for quick disconnection and removal of the first liquid reservoir to permit substitution of another liquid reservoir containing a mass of liquid at high pressure, a second liquid reservoir, a mass of liquid contained in said second reservoir at atmospheric pressure, a liquid delivery line for connecting said second reservoir to the jack cylinder, a pump interposed in said delivery line for the reception of liquid from said second reservoir and for pumping said liquid into said jack cylinder to produce movement of the jack piston relatively to the jack cylinder, said pressure line and said delivery line being independent of each other for introducing liquid into the cylinder from either the first liquid reservoir or from the second liquid reservoir, a by-pass line connected to said jack cylinder and connected to the delivery line at a point by-passing the pump, a by-pass valve normally maintaining said by-pass line closed and adapted to be opened to release liquid from the jack cylinder through the bypass line and the delivery line for return of liquid from the jack cylinder to the second liquid reservoir.

References Cited in the file of this patent UNITED STATES PATENTS 

